Photocatalytic thin film devices

ABSTRACT

Novel photocatalytic devices are disclosed, that utilize ultrathin titania based photocatalytic materials formed on optical elements with high transmissivity, high reflectivity or scattering characteristics, or on high surface area or high porosity open cell materials. The disclosure includes methods to fabricate such devices, including MOCVD and ALD. The disclosure also includes photocatalytic systems that are either standalone or combined with general illumination (lighting) utility, and which may incorporate passive fluid exchange, user configurable photocatalytic optical elements, photocatalytic illumination achieved either by the general illumination light source, dedicated blue or UV light sources, or combinations thereof, and operating methodologies for combined photocatalytic and lighting systems. The disclosure also includes photocatalytic materials incorporated on the surface of packaged LEDs, LED lamps and LED luminaires, with photocatalytic materials incorporated on optically useful luminaire surfaces or on the surface of the remote phosphor. The disclosure also includes ultrathin photocatalytic materials incorporated on surfaces to affect antibacterial and antiviral properties.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. Utility application taking priority from U.S.Provisional application No. 61/893,823 filed Oct. 21, 2013, and hereinincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to novel photocatalytic devices,fabrication methods for those devices, and novel systems that combinelighting and photocatalytic air purification functions.

BACKGROUND References

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The plethora of chemical contaminants in our environment is a majorconcern, and their deleterious health effects are only partiallyunderstood but believed to be enormous. Commercially practicaltechniques for removal of these contaminants are therefore of greatinterest. Examples of contaminants include, but are by no means limitedto formaldehydes, aromatic hydrocarbons, various mitogen oxides,pesticides, specific bacteria, viruses, etc.

Titanium dioxide is the archetypal photocatalyst, due to its highlyoxidizing properties when irradiated by UV light, physical robustness,insolubility in water, low cost, low toxicity and other attributes.Photocatalysis using titanium dioxide (titania, TiO2) has received hugeinterest for purifying gases and fluids, in particular air and aqueousfluids, via oxidizing chemical reactions at a surface, via creation ofelectron-electron hole pairs.

A wide variety of titania-based materials, doping schemes, physicalconfigurations have been proposed to enhance and utilize photocatalysisat TiO2 surfaces, although so far there has not been widespread adoptionof the technology for purification of air, fluids or surfaces. Theinventors of the present invention believe that several technical andeconomic factors have reduced the utility, effectiveness, commercialviability of photocatalytic air purification systems.

Photocatalysis is typically achieved by a low or medium pressure UVlamp, or in some cases a Xenon lamp, irradiating the front surface of aceramic or powder based titania surface, i.e. from the direction of themedium that is targeted to be purified. UV LEDs have also been employed,although these devices typically have very short product lifetimes andare unreliable.

Photocatalysis utilizing titanium dioxide is typically excited byillumination in the UV or near UV 240-400 nm spectral region, which ishazardous to humans, more technologically complicated and more expensivethan visible light based illumination sources.

Other challenges with conventional standalone photocatalytic systemsinclude the difficulty of uniform radiation, purification media (i.e.media to be purified) interfering with illumination, high voltage lamppower supplies and control, mercury content in the lamp, air exchangeand the large system sizes. The need for a dedicated illumination sourceincreases system complexities and therefore reduces the viability ofcommercial devices.

The chemical activation at the surface of a photocatalytic surfaceoriginates with the formation of electron-electron hole pairs that arisefrom optical stimulation. Activation at the surface typically has afinite lifetime that is limited by illumination and recombination ofelectron-electron hole pairs. Mitigation of these effects has beeninvestigated primarily via chemical modification of the titaniaparticles, although there has been no consensus in technical approachfor manufacturing practical photocatalyst materials and systems.

Widespread proliferation of new technologies is often highly constrainedby financial considerations such as return on investment and theavailability of adequate capital. Currently the general lightingindustry (estimated market size over $30B), is undergoing a revolutioncharacterized by both technological and capital investment aspects;adoption of solid state lighting (SSL) is gaining momentum. SSLtechnology has made enormous strides since the invention of efficientblue LEDs in the 1990's, and completely new vertically integrated supplychains have arisen to address the needs for specialized raw materials,opto-electronic semiconductors (LEDs and eventually OLEDs), phosphor andpackaging materials, manufacturing equipment, interconnects, LEDcontrollers and microcontrollers (MCUs), power supplies, fixturing,luminaires, etc.

The inventors of the innovations described herein believe thattechnically superior and commercially viable photocatalytic systems maybe achieved by leveraging semiconductor technology and the capitalinvestment environment of microelectronics and SSL industries.

SUMMARY OF THE INVENTION

One aspect of the invention relates to fabrication methods to formultra-thin and highly uniform photocatalytic materials based on titaniumdioxide, titanium dioxide doped with rare earth oxides, (e.g. TiO2-CeO2or any other lanthanide or combination thereof), with transition metals(e.g. Co, W, V, W, Zr, Cu, Fe Cr) or the aforementioned materialscombined with metal nanoscale or microscale metal particles at thetitania surface, e.g. Pt, Ag, Cu, Fe etc. All of these composite, dopedand metal article containing titanium oxide based materials, includingbut not limited to the stoichiometric TiO2 formulations, will bereferred to as “titania” in the description and claims of thisinvention. Combinations formulated for photocatalytic activity will bereferred to as ‘photocatalytic titania based materials’ in thedescription and claims of this invention. In this context ultrathin maybe defined as the minimum thickness required to exhibit desiredphotocatalytic surface properties, i.e. typically 3-50 nm. physicalthickness. Such ultrathin layers of the subject invention will beparticularly useful when formed on optically useful substrates such asthose with high optical transmissivity, high reflectivity, and highincoherent reflectivity (e.g. scattering surfaces, either Lambertian orotherwise).

These ultrathin layers may also be particularly useful when formed onhigh surface area or high porosity open-cell substrates, for examplethose which have moderate B.E.T. surface area in the range of 5-50 m2/g,or with high BET surface area, e.g. greater than 50 m2/g.

It will be understood to those practiced in the art of photocatalyticmaterials that the subject invention will also be useful and directlyapplicable to photo-electrochemical (PEC) cells, super-hydrophilicsurfaces, antimicrobial surfaces, self-cleaning surfaces and otherrelated applications of titania-based materials.

Photocatalysis is a surface phenomenon, and therefore the thickness ofphotocatalytic material may be very small in order to present a suitablechemically activated surface., i.e. in principle less than 10 nm.physical thickness, It evident that such a titania layer must beadequately uniform in order to take full advantage of a high surfacearea substrate and hence maximize the active area. Microelectronics thinfilm technologies, especially metal organic vapor deposition (MOCVD) andatomic layer deposition (ALD), are particularly well suited todeposition of thin films of materials.

It is desirable that such photocatalytic films be formed with a highdegree of precision in thickness and properties, as well as uniform inthickness across the device and conformal where the substrate hastopological surface enhancement. Suitable methods to form films of thesubject photocatalytic titania based materials include vacuumsputtering, ion beam deposition, chemical vapor deposition(CVD)/metalorganic chemical vapor deposition (MOCVD), and atomic layerdeposition (ALD), in order of increasing inherent uniformity andconformality.

Films of photocatalytic titania based materials may be deposited byvacuum sputtering using metal targets or alloyed metal targets and areactive oxidizing gas such as oxygen. The process may also employ oxidetargets or alloyed oxide targets. In the case of unalloyed targets, thetargets may be used simultaneously or in alternating fashion Vacuumsputtering is carried out at reduced pressures, typically in thepressure range of 10-5 Torr. Ion beam deposition is carried out atreduced pressure and results in very smooth films.

These processes are carried out in a chamber capable of producingsuitable vacuum pressures and the substrate may be stationary or movedin a linear or other manner, and may be called Physical Vapor Deposition(PVD).

Any of these techniques for thin film deposition may individually andcollectively be referred to as “low pressure” deposition techniques inthe description and claims of this invention.

Other “in air” deposition techniques can be used to deposit thephotocatalytic films herein described, such as, but not limited to, spincoating and heat treating, flame jet deposition, and roll coating. Theseatmospheric pressure techniques typically have reduced thickness controland conformality capabilities relative to low pressure techniques, butlower costs for manufacturing as well because the atmosphere for thedeposition process is not highly controlled, as in the case of lowpressure deposition techniques. It is intended that the scope of thisinvention include both low pressure and “in air” atmospheric pressuredeposition techniques for deposition of photocatalytic films.

Deposition of one or more other coatings to modify the opticalproperties of substrates may also be carried out. These additionalcoatings, if any, may be deposited in the same chamber or chambers asthe photocatalytic thin films are deposited in, or in differentchambers. The additional coatings may be deposited by the sametechniques as those which are used to deposit the photocatalytic thinfilms, or may be deposited by different techniques.

CVD, MOCVD and ALD may be carried out with gaseous, solid or liquidprecursors, which may be dispensed to the low pressure coating chamberby passing a carrier gas over the source, or dissolved in solvent forliquid delivery to a vaporizer and thence to the vacuum coating chamber.Suitable precursors include halides, amides, amidinates,beta-diketonates, alkoxides, iminates, kitiminates, guanidinates andvarious Lewis base coordinated molecules. Suitable organic solventsinclude straight and cycling alkanes, alkenes, and alkynes, alcohols,and aromatic liquids. Deposition may be carried out at atmosphericpressure, in which case the gases used for deposition are typicallycontrolled such as to exclude air, or preferably sub-atmosphericpressures.

The deposition of the film via CVD and MOCVD preferably uses precursorswith compatible ligands that do not result in detrimental ligandexchange. Examples of such precursors include Ce(thd)₄ andTi(OiPr)₂(thd)₂, Ce(thd)₃-L and Ti(OiPr)₂(thd)₂, CeNR₁R₂, TiNR₁R₂, whereR₁ and R₂ comprise H, methyl, ethyl, propyl, etc. For ALD, theaforementioned precursors may be used together in dosing pulses tocreate an alloyed film, or separate pulses of Ti and the lanthanide maybe used to create a layered film. Additional precursors suitable for ALDinclude Ti(Cp)₄ and Ce(Cp)₄ along with variously modifiedcyclopentadienyls where H is substituted by alkyls. Ti(OiPr)₄ or otheralkoxides may be used, as well as Ti halides, e.g., TiCl₄, TiBr₄, TiI₄.

Additionally, the CVD/MOCVD process may be carried out in a pulsedmanner in which the precursors are separated from the co-reactant.

Co-reactants suitable for CVD and MOCVD include oxygen and nitrousoxide. For ALD, oxygen and nitrous oxide may be used, or more reactivespecies such as plasmas of the oxidizing gas(es), ozone, or water.

The ultrathin characteristic of the subject photocatalytic material hashigh utility in that the optical function of the substrate/opticalelement may be predominantly unaffected. In some cases the subjectultrathin material may be incorporated and optimized as the outer layerin that element's optical interference coating design.

A related aspect of the invention are fabrication methods to conformallydeposit the subject titania or titania based thin film materials on asubstrate that has a high degree of nanoscale or microscale roughness,in order to increase the surface area of the resultant photocatalytictitania based material and to enhance the photocatalytic effect.

A related aspect of the invention describes fabrication methods to formthe subject photocatalytic titania based materials with acrystallographic structure that is optimized for efficientphotocatalytic activity (e.g. anatase crystal structure) and totherefore enhance the photocatalytic effect.

A related aspect of the invention describes fabrication methods to formthe photocatalytic titania based materials with optical absorptionshifted to longer wavelengths (e.g. >400 nm.) in order to utilizevisible light LEDs to stimulate the photocatalytic effect.

Another aspect of the invention relates to the geometry of the UV orvisible light irradiation, such as from the back surface of a substrate,or via waveguide propagation through the substrate that supports theultrathin photocatalytic titania based material. It is evident that suchtitania based photocatalytic layers need to be extremely thin and highlyuniform in order to allow some fraction the illumination photons toreach and be absorbed near the front surface of the photocatalyticmaterial.

The use of the subject ultrathin catalytic materials on transmissiveoptical elements open many possibilities for purifier designs inapplications where it is constraining, difficult or impossible to usefront surface illumination, i.e. to avoid positioning the UV or visibleillumination system in the medium to be purified. This configuration maybe useful for both gaseous media and liquid media purification.

For purposes of this invention, liquid may refer to any mixtures ofliquids, colloids and solids, capable of flowing via gravity or beingpumped. Said liquids may contain dissolved gasses or solids. In anexemplary embodiment, said liquid is primarily water. Gas may refer toany mixture of gaseous elements, whether free flowing or pumped. Saidgases may include entrained liquid or solid particles. In an exemplaryembodiment, said gas is primarily air. For purposes of this invention,flowable media may refer either to gasses or liquids.

The invention includes monolithic integration of a ultrathin titaniabased photocatalytic material on the surface of a solid state lightemitting device such as an LED or OLED. In this context the LED devicesmay be individually packaged die, multiple die modules, LED lamps (e.g.conventional light bulbs, MR-16s, etc.), lighting fixtures andluminaires. For LED packages and modules, the photocatalytic materialwould be back surface illuminated in these integrated devices. For LEDlamps, fixtures and luminaires, the photocatalytic material may beeither from or back surface illuminated, depending on technical andaesthetic aspects of the device design.

Several aspects of LED lamp products and technology may be especiallyuseful to create fluid purification functionality via incorporation ofultrathin photocatalytic materials on an LED die, module or lampenvelope or luminaire transmissive, reflective or scattering surface.For example, LEDs may have white or blue optical output which may beadapted for purposes of this invention as the photocatalyticillumination source.

Integral LED driver ICs Lamps and high power LED modules oftenincorporate or are packaged with control ICs. In an embodiment of thisinvention, these control ICs, if present, may be straightforwardlyadapted to communicate with and control additional UV LED die and forcontrol algorithms, both being applicable to auxiliary photocatalyticillumination source.

High performance packaged LEDs incorporate physical optics techniquessuch as surface roughening and texturing, in order to increase opticalout-coupling, light output and hence output efficiency. Surfaces of thistype, when modified by the addition of an ultrathin photocatalyticmaterial in an embodiment of this invention, will have larger surfacearea and hence higher purification efficiency.

High performance LED lamps are engineered to remove waste heat, whichwould otherwise cause the device to operate at high temperatures,thereby reducing device lifetime. Airflow parallel to the lamp surfaceis optimized to remove heat. This concept of engineered airflow may beadapted in an embodiment of this invention to efficiently exchange airto be purified at a photocatalytic surface. In a preferred embodiment,that photocatalytic surface may be back surface illuminated, i.e. via atransmissive substrate that has high transmissivity at thephotocatalytic illumination wavelength.

Another aspect of the invention relates to front surface illuminationgeometry of the UV or visible light irradiation. The subject ultrathinphotocatalyst layer may be formed on a highly reflective surface, suchas on a metallic layer, on an all-dielectric interference coating, or ona dielectric enhanced metal reflector, and the photocatalyst-reflectorsystem may be optimized to enhance the photocatalytic effect. Reflectorsurfaces may be formed either on an opaque metallic, plastic or ceramicmaterial via conventional optical coatings or other treatments, or on aglass or plastic transparent surface, employing similar techniques.

A related aspect of the invention utilizes front surface illumination ofa particle, ceramic coated or other preexisting surface that has opticalutility, onto which the titania based photocatalytic surface has beenformed. That surface may have a high degree of optical scattering, e.g.a highly Lambertian scatterer for the visible, ultraviolet or infraredspectral regions. That particle or ceramic coated surface may also be aremote phosphor used in a blue or UV LED pumped white light luminaire,i.e. a phosphor that is not configured on the LED package material, butat transmissive, reflective or scattering surfaces at distancestypically ranging from 1-200 mm from the packaged LED die or LED array.

Several further aspects of the invention incorporate photocatalyticfluid purification systems that utilize the photocatalytic materials andillumination inventions cited above. One such invention relates topurification of surfaces of medical tools, kitchen counter top surfaces,or other implements or everyday items, either during use or when instorage.

Another aspect of the invention relates to air purifier systems thatincorporate the inventions cited above. These air purifier systems maybe provided as standalone systems, or as systems that are integral to aroom or isolated space that requires ambient conditions, walls and otherconfining surfaces to have a high degree of purity with respect tocontaminating chemicals or contagion.

It is evident that such purification systems will maintain extremely lowlevels of contamination on the surfaces of the system and hence thesubject inventions include surface purification systems.

Related aspects of the invention include purification of other flowablemedia besides air, such as, but not limited to, water, other aqueousliquids including in-vivo fluids, and non-aqueous liquids.

Several related aspects of the invention are methods to enhance thephotocatalytic purifying process by increasing the exchange of flowablemedia at the purifying photocatalytic surface or substrate. In thecontext of this patent, substrate refers to any object or structure ofany shape on which a photocatalytic thin film may be disposed. Thissubstrate may have simple geometric forms, such as a flat plane orsimple curves, or may be shaped into more complex geometric forms withhigher surface area such as, but not limited to, fins, channels, ortubes. These complex geometric forms may serve several purposes, suchas, but not limited to, increasing surface area of the photocatalyticfilm, improving or controlling flow of the flowable media, and sheddingor transferring heat. A surface may be considered a complex geometricform if it has at least 1.5× the surface area of a simple geometricform, such as a plane, a cylinder or a sphere.

Flow of the flowable media to be purified may take place by means suchas, but not limited to, convection, gravity, fans or pumping. Flow maytake place past structures such as, but not limited to, fins orchannels. Flow may also take place through structures such as tubes,which may be regular in shape and form or which may be irregular, suchas through a porous media. In a preferred embodiment of this invention,the structure comprises an open celled foam. Flow may be accomplished byactive fluid pumping systems, or by passive means, or by a combinationof active and passive means. Passive means may increase movement,turbulence and exchange of fluid via convection, resulting from theshape and orientation of the photocatalytic surface, and/or includinglocalized introduction of heat to the fluid. Such heat may be waste heatfrom the UV or visible photocatalytic illumination source, waste heatfrom an integral lighting system, or from other sources. Systemsincluding, but not limited to, pumps, directional convection, valves,fans, pressure differences, and gravity may be used to achieveanisotropic flow of the flowable media, that is, flow primarily in aparticular direction past the photocatalytic device or film.

A further aspect of the invention relates to photocatalytic air purifiersystems that incorporate combined purifier and lighting functions. Thesecombined lighting and photocatalytic purification systems mayincorporate either back surface or front surface illumination of thetitania based photocatalytic material. Such combined function systemsmay either be for specialized use, such as, but not limited to, inoperating room or other clean room environments, or for generallighting, for example in private residences, schools and workplaces.

The invention includes operational modes for the subject photocatalyticfluid purification systems. In some cases for either back surface orfront surface photocatalytic illumination of the photocatalytic surface,such as in the case where UV or visible irradiation is employed, theillumination may be unhealthy or unpleasing for people. In such casesthe illumination may be intermittently turned on & off based on dailyschedules, detection of people via movement or by electronic ID schemes,or by other means and logical schemes.

In combined purification and lighting systems, the invention includescombination of photocatalytic illumination sources with the spectrallybalanced general illumination lighting sources. In one example, for anLED lighting array, white light LEDs may be packaged together with shortwavelength LEDs (e.g. blue, violet or ultraviolet emitters) such asInGaN LEDs with emission wavelength less than 450 nm. that have nophosphor. Such short wavelength LEDs in the array may be controlledseparately as described above or as based on other logical schemes.

The present invention may include a number of the inventive elementssummarized above, in a variety of combinations and configurations.

The Inventions summarized above are illustrated in several examples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a back surface illuminated photocatalyticdevice, illustrating various geometries to couple the light sourceconfigurations.

FIG. 2 is a schematic of back surface illuminated photocatalytic device,illustrating a conformal thin film photocatalytic material on a highsurface area optically transmissive substrate.

FIG. 3 is a schematic of a combined lighting and air purification systemutilizing front surface illumination of the subject photocatalytictitania based material formed on a reflector.

FIG. 4 is a schematic of a combined lighting and air purification systemutilizing front surface illumination of the subject photocatalytictitania based material formed on a remote phosphor in an LED poweredwhite light luminaire.

FIG. 5 is a schematic of a combined lighting and air purification systemutilizing a predominantly white lighting luminaire and an opticallytransmissive element that supports the subject titania photocatalyticmaterial.

FIG. 6 is a schematic of a combined lighting and air purification systemutilizing passive (i.e. convective) means to exchange ambient fluidsduring purification.

FIG. 7 is a schematic of a combined lighting and air purification systemutilizing. an array of LED white light emitters in a decorative andlight directing luminaire assembly.

DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS THEREOF

The present invention relates to novel photocatalytic materials,fabrication methods for those materials, and novel photocatalyticdevices and systems. The invention also describes an apparatus andassociated methods of construction and operation for combining aphotocatalytic thin film with a light source in order to purify aflowable media. Particular embodiments will focus on LED light sourcesand use in air, but any of the embodiment disclosed herein may becombined in any fashion in order to carry out the purposes disclosedherein.

In one aspect, the invention relates to the use of vapor phase or lowpressure methods to deposit a uniform layer of titanium dioxide film, amixed titanium oxide lanthanide oxide film, or a mixed film with metalparticles incorporated on our near the surface. Lanthanides include La,Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm Yb, and Lu. These methodsinclude, by way of example, sputtering, evaporation, metalorganicchemical vapor deposition (MOCVD), and atomic layer deposition (ALD),and they typically take place in a chamber at pressures belowatmospheric pressure and with a controlled atmosphere.

Evaporation is the simplest method and co-evaporation of oxide sourcesmay be used to deposit a uniform substantially homogeneous film over aplanar substrate. Alternatively, elemental sources may be used in anoxidizing environment. Sputtering from a uniform or composite target mayalso be used on planar surfaces and to some degree on curved surfaces.

MOCVD has the ability to form a uniform layer on curved surfaces andsurfaces with complex geometry that have a high degree of topography. Inthe case of MOCVD, the deposition temperature is kept in a range whereconformality is high and the deposited film is substantially amorphous.In one embodiment, a photocatalytic film, ceria doped titania, isdeposited by MOCVD. The precursors, Ce(thd)₄ and Ti(OiPr)₂(thd)₂ aredissolved in an organic solvent and delivered to a vaporizer inmaintained at a temperature in the range of 150-250° C. Argon carriergas is flowed through the vaporizer at 100-200 sccm and into adeposition chamber where the substrate is held at a temperature of450-650° C. and a pressure between 1 and 20 Torr. Oxygen is flowed as aco-reactant gas at between 400 and 1000 sccm. A thin ceria doped titaniafilm is deposited on the substrate. The thickness of the ceria dopedtitania film may be between 1 and 30 nm.

Atomic layer epitaxy (ALD) may be used to deposit uniform layers ontothe aforementioned surfaces and also on highly curved surfaces or intofeatures of very high aspect ratio (e.g., >3:1). In one embodiment thephotocatalytic film is deposited by ALD. The precursors, Ce(Cp)₃ andTi(Cp)₄ are transported together by argon carrier gas flowed at 100-200sccm and into a deposition chamber where the substrate is held at atemperature of 150-450° C. and a pressure between 1 and 20 Torr. Thecombined Ce(Cp)₃ and Ti(Cp)₄ gas phase precursor is delivered for aspecific time, followed by an inert gas purge, then oxygen is flowedthrough a water bubbler held at between 5-15° C. as a reactant gas,followed by an inert purge. Reactant and inert gas purge flows arebetween 200-1000 sccm. This set of pulses is repeated until a thin ceriadoped titania film is deposited on the substrate. In a preferredembodiment of this invention, the ability of ALD to deposit layers onextremely high aspect ratio structures may be used to form aphotocatalytic thin film on an interconnected porous structure such as,but not limited to, that of an open celled foam.

In another embodiment, the ALD process employs separate pulse trains ofCe(Cp)₃ and Ti(Cp)₄ precursor, each followed by the oxidizing and purgesteps as described above. Composition of the resulting titania-lathanidematerial would in those cases be determined by the ratio of Ce(Cp)₃ andTi(Cp)₄ ALD cycles.

MOCVD may be carried out with solid sources held in bubblers throughwhich a carrier gas is flowed to convey the source to the depositionchamber. The sources may also be dissolved in an organic solvent asindividual sources or combined together. Key criteria of a solventsystem are (1) high boiling point to reduce the chance of flash off ofthe solvent, (2) high solubility for the compound, (3) low cost. Usefulhydrocarbon solvents may include, for example: octane, decane,isopropanol, cyclohexane, tetrahydrofuran, and butyl acetate or mixturescomprising these and other organic solvents. Lewis base adducts may alsobe incorporated as additions to the solvent(s) for beneficial effects onsolubility and to prevent possible oligimerization of the precursormolecules. Examples of useful Lewis Bases include polyamines polyethers,crown ethers, and the like. Pentamethylenediamine is a one example of apolyamine. Examples of polyethers include various glymes such as mono-,di-, tri-, and tetraglyme.

Most MOCVD processes have two temperature regions of interest: a surfacereaction kinetic limited range at lower temperature and a mass transportlimited range at higher temperature. Co-reactants useful for forminghigh quality mixed ceria-titania films include oxygen and nitrous oxide.In general, there is a large excess of oxygen in the process, so thatcarbon incorporation in the film is minimized. The primary objective inthe present invention is the formation of a film of as homogenous anature as possible, preferably a film of substantially anatase crystalstructure.

Depending on the substrate and titania-lanthanide film composition, seedlayers or other thickness dependent inhomogeneities may be utilized toenhance formation of the anatase phase, optimize absorption of thephotocatalytic illumination, increase surface hardness or durability, orto otherwise enhance the photocatalytic effect. In this context seedlayers may be introduced as part of an ALD, MOCVD or PVD process, or viaan different process.

In some embodiments, lateral composition, topographic or microstructuralinhomogeneities may be engineered in the surface, in order to achievespecific hydrophilic or hydrophobic properties in order to modify fluidflow characteristics at that surface.

The deposition system may have an automated throttle valve that allowspressure to be controlled independently of flow. In this way, residencetimes can be manipulated more directly. The hot-wall type reactor is onetype of reactor that may be used to deposit the subject films.Alternatives include batch hot-wall reactor or warm-wall showerhead typereactors.

Useful MOVCD process conditions span a range of temperature from 250°C.-650° C. and total pressure between 0.5-50 Torr. Preferably, theprocess temperature is below 500° C., and pressure is between 1 and 10Torr.

The use of ALD to create a crystalline mixed titania-ceria film affordsa higher degree of conformality than MOCVD. ALD also offers thepossibility of batch processing. ALD is a surface saturation limitedmethod for depositing thin films in which alternating pulses ofreactants are introduced to the process, generally separated by an inertpurge pulse. Typically, one reactant contains the cation and a secondreactant contains the anion (oxygen in this case). The advantage of ALDis that each layer formed by a surface saturation limited cationcontaining layer, that is subsequently purified and/or oxidized by thesecond reactant pulse. A typical ALD cycle consists of the firstreactant pulse, a purge pulse, the second reactant pulse and anotherpurge pulse. The cation containing layer may be formed using anysuitably volatile precursor, e.g., a metalorganic, a metal halide, metalhydride, or combinations thereof.

Forming a composite or multicomponent oxide film by ALD may beaccomplished using different approaches. In the first approach, thesubstrate is exposed to two or more metal cations simultaneously. Theratio of cations in the precursor (reactant) is chosen to achieve thedesired ratio of cations in the film.

In the second approach, the cations may be alternated by ALD cycle. Thedesired composition is achieved by choosing the ratio of one cationcycle to the other. As an example, for a 25% alloy of species B in oxideA, 1 cycle of species B would be followed by 3 cycles of species A.

Similar precursors to the MOCVD process may be employed for ALD.Cyclopentadienyl coordinated metal precursors may also be advantageouslyused for ALD of ceria-titania films. For the case of simultaneousintroduction of the metal containing precursors, source materials arechosen so that there is compatibility between the chemistries such thatunwanted ligand exchange is prevented. Process conditions favorable forALD are in the temperature range of 100-375° C. with pressures in therange of 1-5 Torr. Co-reactants (oxidizers) include oxygen, nitrousoxide, plasmas of these gases, ozone, or water. We note that surfacepreparation (termination) can be very important in ALD. Pre-treatmentsto promote uniform nucleation include aqueous acids/bases compatiblewith the substrate and that result in —H or —OH termination of thesubstrate surface.

Anion doping of the titania film may also be employed in the films ofthe subject invention e.g., incorporation of nitrogen via either ALD orMOCVD. This may be accomplished by using a nitrogen containingco-reactant, e.g. ammonia or other amines, nitrogen oxides, plasmas orcombinations of these, with or without oxidizing reactants.

Other materials may be incorporated below, above, or in the oxide film.An example is a metal that substantially maintains its metalliccharacter that may act in an optically or photocatalytically enhancingmanner. The metal may be deposited by any suitable means, includingevaporation, sputtering, chemical vapor deposition, or ALD. They may bedeposited on the substrate before film deposition takes place, duringfilm deposition, or after film deposition, or in any combinationthereof. Noble or precious metals that strongly segregate from thealloyed oxide may be used, for example Pt or Ag. These could beincorporated into the oxide ALD process or separately using theaforementioned methods. Non-strongly segregating metals may also beused, provided that the processing temperatures of the oxide filmdeposition method do not cause the metal to incorporate into the oxidesuch that it loses its metallic character. Optionally, thermaltreatments such as annealing may be used to promote agglomeration of themetal or de-wetting to form island structures.

Metallic particles may be dispersed onto the film by depositing themetal by physical vapor deposition means such as, but not limited to,evaporation or sputtering. The metallic particles may includetransition, precious, or noble metals. For example, Pt may be depositedby vapor phase means. In the case of evaporation, the metal may bedeposited by resistive heating of a charge or by electron beam heatingat reduced pressure. Preferable reduced pressures are below 10-3 Torr.Sputtering of Pt may be carried out at reduced pressure. In eitherevaporation or sputtering, the metal may be deposited on theTi-lanthanide film at room temperature or at elevated temperature. Thefilm is heat treated to induce de-wetting to form small islands. This ispreferably performed in a oxidizing ambient, the temperature and degreeof oxidizing atmosphere chosen to be compatible with the substrate uponwhich the titania film has been deposited. The island size defining thelateral dimensions of the metal particles may be between 200 nm and 1500nm is preferably between 5 and 50

Doping of the photocatalytic titania based materials with metallicspecies segregated on an atomic scale, such as Ag, Au, Cu, Pt and Fe,may also be accomplished using the aforementioned techniques.

Incorporation of metal particles in such titania based photocatalyticmaterials may serve three separate and functionally complementaryfunctions:

-   -   1) Enhancement of optical absorption. Ag is of particular        interest because of the surface plasmon resonances on the near        UV-blue spectral regions    -   2) Retardation of recombination of photocatalytic illumination        generated electrons and electron holes, especially Pt and        platinum group metals. This is a well known effect in particle        based catalyst systems.    -   3) Complementary antimicrobial effects of metals that are highly        electronegative, especially Cu and Ag.

The present invention may utilize one or several species or size scalesof metal particles incorporated in a thin film titania or doped titaniaor composite titania thin film matrix, to achieve one or more of thesethree phenomena depending on the desired purpose or application. ALD ofcomposite materials of this type are of particular interest based on thecapability of that technique to form precise nano-laminates ofdielectric and metal composite structures.

Other aspects of the subject invention include geometric and physicaloptics schemes to exploit the surface chemistry and hence purificationattributes of ultrathin titania based photocatalytic materials asdescribed above. We note that the principles described below may also beutilized with previously identified photocatalytic materials, both thosebased on titanium dioxide and also based on other materials.

The photocatalytic materials of the present invention, such as thosedescribed above, and others that include, may be deposited on varioussubstrates and in a variety of configurations also identified in thepresent invention, thereby enabling a range of photocatalytic fluidpurification devices. Photocatalytic purification may be used to removeorganic and other chemical species from a fluid that may be eithergaseous (e.g. air) or liquid (e.g. water). Impurity species in such afluid are brought into near proximity or adsorbed at the photocatalyticsurface, and are subsequently chemically dissociated.

In general gaseous fluids to be purified by such devices include ambientair in residential, commercial, industrial and public buildingenvironments, as well as specialized application environments thatinclude manufacturing clean rooms, hospital operating and recoveryrooms, etc. Liquid fluids to be purified include drinking water as wellas in-vivo and in-vitro purification and chemical processing in medicaland biomedical applications.

In general, a photocatalytic fluid purification system requires threeconditions:

-   -   I) a photocatalytic surface    -   II) a source of radiation to excite the photocatalytic effect        (“photocatalytic illumination”)    -   III) a fluid exchange means to move fluid across the surface of        the photocatalytic material.

The photocatalytic surface may be a solid substrate that has had one ormore surfaces modified to incorporate photocatalytic material. Dependingon the application, the fluid meant for purification, the surface areanecessary for efficient purification, the geometry and wavelengths ofthe incident photocatalytic illumination, a variety of substrates may beemployed.

The fluid exchange means III is comprised of mechanical confinement tochannel the fluid exchange flow, and a way to drive that flow.

For titanium dioxide photocatalytic materials, and for some embodimentsof the present titania based photocatalytic materials, photocatalyticillumination is necessarily in the 200-400 nm. spectral region. Fortitania-lanthanide and titania-transition and metal particle or metaldoped materials of the present invention, photocatalytic illuminationmay be in the 400-450 nm. spectral region.

For some fluid purification applications, either gaseous or liquidpurification, the photocatalytic material and fabrication of thatmaterial may be advantageously utilized on substrates of various shapesand surface finishes that facilitate conditions II and/or III in thepreceding paragraph.

Combined Lighting and Purifications Functions

There are a range of embodiments for the present invention thatincorporate combined lighting and air purification functions. In thoseapplications and configurations certain attributes of the lightingsystem may be advantageously adapted to provide either Condition IIand/or Condition III as described above.

These combined lighting and purification functions may be enabled byfabricating a photocatalytic material on surfaces that have opticalutility for the lighting device, as a partial or comprehensive way tosatisfy Condition II. These “optically useful surfaces” may be eitherspecularly reflective, specularly transmissive, non specular, (i.e.scattering) transmissive or reflective surfaces, the surface of anup-wavelength converting phosphor (i.e. Stokes shifting), orcombinations of these optical surface types, which are incorporated inthe lighting device. In such cases in which the photocatalytic materialis applied to an optically useful surface, such material may be thetitania based material of the present invention, or anotherphotocatalytic material that is known to in the art.

One potentially useful attribute of a lighting device or light source isits optical output (“lighting illumination”), which is typicallybroadband in the 400-700 nm (“visible spectrum”) spectral region.Whereas incandescent, metal halide and fluorescent light sources tend toemit lighting illumination that is somewhat broadband over the visiblespectrum, light emitting diodes (“LED”) used in lighting often have astrong blue or violet spectral emission.

Although the majority of the discussion below addresses adaptations anduse of LED light sources, we emphasize that any light source may inprinciple be utilized if it offers suitable short wavelength output, orhas other attributes as described below.

White light emitting LEDs typically employ either one of two white lightgenerating mechanisms. The most common mechanism uses a blue/violet LEDthat excites a phosphor; the resulting lighting illumination iscomprised of the original blue/violet light, mixed with longerwavelengths in the green, orange and red portions of the visiblespectrum.

The second, less common white light generating mechanism employs threeLEDs, typically red, green and blue (RGB). In these cases the emissionof these RGB spectral components are mixed to generate white light, andin some LED devices the spectral irradiancy of each RGB component may becontrolled by a microcontroller, e.g. using pulse width modulation, inorder to generate a continuum of white light color temperatures ordifferent colored light entirely.

For either of these two white light generating LED mechanisms, the shortwavelength components of LED lighting illumination will typically be inthe 400-470 nm. spectral region. In the former of the two mechanisms,the short wavelength phosphor pump wavelength may also be in theultraviolet, with wavelength in the 300-400 nm spectral range. Ingeneral, LED light sources that have stronger relative output in the360-420 nm spectral range may offer greater utility and flexibility toincorporate the inventive concepts herein.

In some embodiments of the present invention, certain short wavelengthspectral components of the lighting illumination may usefully also serveas the photocatalytic illumination. Although LED lighting devices areparticularly well suited to provide such short wavelength photocatalyticillumination, we note that other lighting illumination sources may alsobe utilized in the subject invention.

Combined lighting and purification systems that utilize spectralcomponents of the lighting illumination to serve as the photocatalyticillumination source, without the use of auxiliary photocatalyticillumination sources, will be denoted as “Mode 1”.

In related and complimentary embodiments, the photocatalyticillumination may be completely provided by an auxiliary photocatalyticillumination source, and the lighting and purification functions wouldin those cases share other attributes of the combined system such asoptically reflective, transmissive, scattering surfaces, and fluid flowcontrolling surfaces. The lighting illumination may also be usefullycombined with an auxiliary photocatalytic illumination source, in orderto increase the sum total of the photocatalytic illumination. Combinedlighting and purification systems that incorporate an auxiliaryphotocatalytic illumination source will be denoted as “Mode 2”.

Other embodiments of combined lighting and purification systems mayadvantageously employ certain heat dissipation and fluiddynamics/confinement attributes of select lighting device as a means tocompletely or partially satisfy the photocatalytic purificationCondition III as described above.

In general, all electrical powered light sources are inefficient to someextent, in that significant electrical input power is not converted intovisible light (lighting illumination), but is instead converted tothermal energy that heats the light source. This is especially true fortungsten-halogen lamps, incandescent lamps, ceramic metal halide sourcesand solid state light (SSL) sources such as LEDs and organic LEDs(OLEDs). Higher temperature operation is typically not a major issue forall of these except SSL sources, since increases in the sourcetemperature shift the predominant blackbody radiation to shorterwavelengths, thus increasing the visible light output to some extent. Onthe other hand, SSL sources such as LEDs are deleteriously affected byoperation at high temperature; device lifetimes are dramaticallyreduced. Therefore, LED lighting devices, especially high brightnessLEDs (HB-LEDs), are designed and configured with intrinsic coolingfeatures. Typically the LED packaged die is attached to a heat sink basein a high thermal conductivity structure, and the base is in turnattached to cooling fins and/or a large thermal capacity structure thatcan dissipate the heat. Certain LED light sources, especially LED lampsand LED luminaires, employ fairly sophisticated designs to remove theLED waste heat using convective flow.

One embodiment of the subject combined lighting and photocatalyticpurification systems is to take advantage of the waste heat and toharness the resultant convective flow across both optically useful andconvective flow confining surfaces in lighting devices, especially forLED lamps and luminaires. There are a wide variety of convectivecooling/air exchange schemes that may be established in concert withoptical surfaces configurations, and several such designs are providedin the Embodiments. These embodiments are in no way limiting as to howthe inventive design principles may be utilized in these types ofdevices and systems.

Convective flow across heated surfaces in such devices may in some casesbe augmented with mechanically driven flow such as from an electricalblower, or in some cases the waste heat may be predominantly driven beauxiliary blower systems. The exhaust for LED lamps and luminaires,which will be made up of partially purified input air, may directlyenter the upper regions of that room, may be recycled and reintroducedto the photocatalytic surface, or in the case of recessed ceilinglighting, it may be delivered back to that room or another space by aduct, or system of ducts. Such ductwork may transport the purified aireither from one of the subject devices, or from a system of manydevices, as in a room with multiple ceiling recessed luminaires, forexample.

We note that although the discussion is primarily using LED lightsources as an example, many other light source types may be used to takeadvantage of these inventive principles. In particular, fluorescentlight sources are well suited to take advantage of this invention, asthey may be designed to emit short wavelengths of light which may beuseful to stimulate the photocatalytic effect. As with the LEDembodiments, photocatalytic thin films may be directly integrated withthe light emitting object, or may be present on a reflector or on atransparent or translucent diffuser sheet near the light emittingobject. Such a reflector or diffuser sheet may, regardless of the lightsource, be designed for insertion into a system having a light source,without replacement of the entire light fixture or luminaire.

Many LED lighting devices that may be utilized to affect the combinedlighting and purification functions described above. These LED lightingdevices include Packaged LEDs, LED Arrays, LED lamps and LED Luminaires.Each of these types of LED lighting devices may employ the subjectinventions in specific ways as appropriate to address specificapplications and product markets. Some possible embodiments to utilizethese LED light sources in fluid purification functions are described inthe attached Table.

LED light sources and configurations for combinedlighting-photocatalytic utilityThree criteria for photocatalytic fluid purification are:

a photocatalytic surface

a source of radiation to excite the photocatalytic effect(“photocatalytic illumination”)

a fluid exchange means to move fluid across the surface of thephotocatalytic material.

Two Modes to provide Photocatalytic Illumination in a combinedLighting/Photocatalytic purification system are:

Mode 1

Combined lighting and purification systems that utilize spectralcomponents of the lighting illumination to serve as the photocatalyticillumination source, without the use of auxiliary photocatalyticillumination sources.

Mode 2

Combined lighting and purification systems that incorporate an auxiliaryphotocatalytic illumination source that provides either all or afraction of the photocatalytic illumination. In the case of thatauxiliary source providing a fraction, the balance of the photocatalyticillumination would be provided by violet or blue spectral components ofthe lighting illumination.

TABLE 1 Light source Photocatalytic purification criteria applicationCondition I: Condition II: Condition II: LED light Light source forphotocatalytic Photocatalytic Photocatalytic Fluid exchange source typedescription purification material illumination means Packaged Single LEDdie Packaged Photocatalytic Mode 1 Light Extrinsic to light blue or(emission LED is material formed on source directly source. violet LEDwavelength 400-450 nm.) incorporated outer surface of excites back Oneembodiment is in a in a fluid transparent surface of a liquid flowconventional flow- package substrate. photocatalytic component madepackage. purification Material is titania- material (substrate fromfused silica or system, based and optically side), via other materialsthat preferably absorbing at LED transmission transmit the liquid, dueemission through substrate. photocatalytic to the wavelength.illumination, with relatively the interior small area of surfaces of theflow packaged passages coated LED. with an ultrathin Packaged Single UVLED die Packaged Photocatalytic Mode 1 Light titania based UV LED(emission LED is material formed or source directly photocatalyticwavelength 200-400 nm.) incorporated deposited on outer excites backmaterial. The in a in a fluid surface of UV surface of blue/violet or UVconventional flow- transparent silica photocatalytic light source ispackage. purification glass cover plate or material (substrate coupledinto a solid system, dome. Material is side), via portion of the silicapreferably titania-based and transmission flow element and liquid, dueoptically absorbing through substrate. this photocatalytic to the at LEDemission illumination is relatively wavelength. confined within thesmall area of element via wave- packaged guiding and/or LED. reflectivemeans. A related embodiment is a silica based microfluidic waveguidestructure, with blue/violet or UV LED radiation coupled into the silicaand propagated via waveguiding and reflective structures to thesubstrate side of the photocatalytic material deposited in themicrofluidic flow channels. Packaged A blue or violet or Blue-Photocatalytic Mode 1 Light Extrinsic to light White LED nearultraviolet violet/phosphor material formed on source directly source[Blue-violet LED die mounted White outer surface of excites backLED/Phosphor] in a suitably packaged transparent surface of transparentLED is package substrate. photocatalytic package such as incorporatedMaterial is titania- material (substrate epoxy or silicone. in a basedand optically side), via A wavelength combined absorbing at LEDtransmission down-converting lighting & emission through substrate.phosphor is fluid flow- wavelength. typically purification impregnatedor system. otherwise incorporated in the transparent epoxy. White LED Anintegral Blue- Photocatalytic Mode 1 Light Extrinsic to light arrayassembly of violet/phosphor material formed on source directly source[Blue-violet multiple blue-violet White outer surface of excites backLED/Phosphor] LED die in a single LED array is transparent surface ofpackage, or incorporated package substrate. photocatalytic multiplepackaged in a Material is titania- material (substrate LEDs, mounted oncombined based and optically side), via a board, a flexible lighting &absorbing at LED transmission membrane or some fluid flow- emissionthrough other integrating purification wavelength. transparentmechanical system. substrate. support, e.g. chip- Alternatively, the onboard (COB). blue or preferably LED arrays may violet spectralintegrated, components of the typically on a lighting board, withillumination may electrical driver, be incident on circuitry, and inphotocatalytic some cases surfaces on a lamp microcontroller or orluminaire. ASIC dimming and color control, optics and other systemcomponents. LED modules that produce white light may be either Blue-violet LED/phosphor or RGB. Alternatively these functions may beprovided on a separate board and incorporated with the array in a lampor luminaire. White LED An integral Blue- Photocatalytic Mode 2 UVExtrinsic to light array assembly of violet/phosphor material formed onLEDs are source [Blue-violet multiple blue-violet White outer surface ofincorporated as LED/Phosphor] LED die in a single LED array istransparent some fraction of package, or incorporated package substrate.the blue-violet multiple packaged in a Material is titania- LED array,and LEDs, with combined based and optically are separatelyphotocatalytic lighting & absorbing at LED powered and illuminationfluid flow- emission controlled, with producing UV purificationwavelength. the UV LEDs also system. photocatalytic incorporated in theillumination array. The UV incident on the LEDs may be in back surfaceof the UV-A (315-400 nm the photocatalytic wavelength), material(substrate UV-B (280-315 nm) side), via or UV-C (100-280 nm)transmission spectral through ranges as transparent appropriate tosubstrate. efficiently produce Alternatively, the the photocatalytic UVillumination effect. may be incident on photocatalytic surfaces on alamp envelope or in a luminaire, as below. White LED An integral RGB LEDPhotocatalytic Mode 1 Blue or Extrinsic to light array assembly of red,array is material formed on violet emitting source [RGB] blue and greenincorporated outer surface of LEDs in the array LED die in a single in atransparent are preferentially package, or combined package substrate.powered and are multiple packaged lighting & Material is titania-incident on the LEDs, mounted on fluid flow- based and optically backsurface of a board, a flexible purification absorbing at LEDphotocatalytic membrane or some system. emission material (substrateother integrating wavelength. side) which has mechanical been depositedon support, e.g. chip- the epoxy on board (COB). package, viatransmission through that transparent substrate. Alternatively, the blueor preferably violet spectral components of the lighting illuminationmay be incident on photocatalytic surfaces on a lamp or luminaire. WhiteLED An integral RGB LED Photocatalytic Mode 2 UV Extrinsic to lightarray assembly of array is material formed on LEDs are source [RGB]multiple LED die incorporated outer surface of incorporated with in asingle package, in a transparent the RGB LED or multiple combinedpackage substrate. array, and are packaged LEDs, lighting & Material istitania- separately mounted on a fluid flow- based and optically poweredand board, a flexible purification absorbing at LED controlled. Themembrane or some system. emission UV photocatalytic other integratingwavelength. illumination mechanical incident on the support, e.g. chip-back surface of on board (COB). the photocatalytic material (substrateside), via transmission through transparent substrate. Alternatively,said UV illumination may be incident on photocatalytic surfaces on alamp or luminaire. LED lamp An integrated & Combined Photocatalytic Mode1 or Mode Fluid flow across completely self- lighting & material formedon 2 Blue violet or the surface of a contained LED fluid flow- outersurface of UV spectral lamp or a nearby light source, often purificationlamp envelope, on components optically referred to as a system.luminaire generated by transmissive flow light bulb, MR-16, reflective,LEDs or arrays, as confining surface PAR, etc. It is transmissive orabove, are (e.g. a transparent comprised of a scattering surfacesincident on the or scattering packaged LED or or on a user lamp envelopeor transmissive flue or LED array, and configurable onto retrofittedconfigurable globe, electrical power retrofit optical or optical and/ormay be achieved circuitry for mechanical fluid flow by convection, andvoltage conversion, element. constraining the design of thatrectification and In general the mechanical element may be constantcurrent thickness of the elements. optimized for generation. Thesephotocatalytic For Mode 2, i.e. maximum fluid functions may alsomaterial on for cases where exchange and be integrally optically usefulUV auxiliary turbulence at the provided as an surfaces, photocatalyticsurface of the LED module (as (especially illumination is photocatalyticabove). The lamp transmissive or used, borosilicate surface. is alsocomprised metallic reflectors glass, plastic or of enclosing in the lampor other UV mechanical luminaire) is on the absorbing structure(s) &order of 10 nm., elements may be optical element(s) i.e. <λ/20 opticalemployed to to scatter, reflect or thickness for most prevent UV fromtransmit the of the visible escaping to the lighting spectrum, in orderlocal illumination to have a negligible environment, and LED A completeCombined effect on intended to prevent that For luminaires, luminairelighting lighting & optical properties threat to people or fluid flowmay be assembly/system, fluid flow- of that surface. the environment.similarly optimized (e.g. recessed 1′ × purification When formed on aAlternatively across the 4′ or 2′ × 4′ ceiling system. the surface of athese UV LED photocatalytic or wall panels, dielectric enhanced elementsmay surfaces on recessed lighting, metal reflector or have scheduledreflective, track lighting, floor an all dielectric on-cycles and/ortransmissive or lamps or table reflector, the brief duration inscattering surfaces, lamps, operating subject titania order to achieveand driven by room lighting based the same result. either purelyfixtures, etc.) photocatalytic convective forces, utilizing one ormaterial may be or an external more LED arrays incorporated into blower,either and/or LED lamps the interference locally at the & lampfixturing, coating design and luminaire, or transmissive, thereflector's centrally for an reflective or optical properties assemblyof scattering optical and color luminaires, or by a elements, appearancemay be combination of mechanical optimized with the these. fixturing,and incorporated electrical power ultrathin titania and controlsmaterial, based on interface. standard thin film design techniques.

Surface Purifications Functions

In general, a photocatalytic surface purification system requires twoconditions:

-   -   I) a photocatalytic surface    -   II) a source of radiation to excite the photocatalytic effect        (“photocatalytic illumination”)

Healthcare Associated Infections (HAI) are a major problem thatthreatens life and increases costs of healthcare. The CDC estimates thatin the U.S. there are 1.7 million hospital-associated infectionsannually, contributing to 99,000 deaths. One primary transmission modefor these infections involves contact with contaminated surfaces, wherebacteria and viruses can reside for days or even weeks on touch surfacesnear the patient. MRSA, C. Difficile, MDRA and Staphylococcus areparticularly dangerous and stubborn contagions that may reside onsurfaces close to a patient. Many types are difficult to attack withantibiotics, and antibiotic resistance is spreading to Gram-negativebacteria that can infect people outside the hospital.

Outside the healthcare world, there are a similar and increasing rangeof opportunistic mass-infections as evidenced by recent Norovirusoutbreaks on cruise ships. These outbreaks may be spread by viruses,bacteria and spores that propagate both airborne and from surfaces tosurface.

It is well known that many standard disinfecting regimens (typicallyliquids comprised of bleach or hydrogen peroxide) may leave a residualcontagion on a surface, which is known as “Bioburden”. Bioburden iscomprised of biofilm or planktonic species residing at a surface that isnominally ‘clean’. Its presence may be due to failure of hospital staffto follow standard procedures, species with exceptional physical,chemical and biological robustness, or a combination of those. There areseveral disinfectant treatments that are receiving wide attention asways to augment liquid treatments. UV-C radiation, ozone anddisinfectant vapors or mists are known to be very effective, but arehighly hazardous and are only viable when a hospital room has beenvacated.

Antimicrobial, or ‘self sterilizing’ surfaces are highly desirable tocomplement standard cleaning. They act continuously, and ideally theyshould have a high killing efficiency for a broad range of bacteria,viruses and spores, and be non-toxic to humans. Silver and coppercontaining surfaces are the most widely investigated, but these haveshortcomings including toxicity, cost and questions about long termefficacy, due to adaptation of bacteria.

The ultrathin titania photocatalytic materials and illumination schemesof the subject invention may be incorporated in a wide range of devicesin order to effect or enhance antimicrobial characteristics of surfaces.These materials may be directly applied to solid surfaces of interest,or applied to flexible polymeric materials that are subsequently appliedto surfaces or formed into those products directly.

In one embodiment, these products may be incorporated in “high touch”surfaces, surfaces which have a great deal of contact by humans.Examples of these products include, but are not limited to: personal orcommercial devices, such as cell phones and smartphones, tablet andcomputer touchscreens and keyboards, hospital objects, such as bed handrails over-bed tables, doorknobs, elevator buttons, escalator or stairrails, writing implements, medical tables, instrument panels, andprotective face masks, and in-vivo devices including but not limited tojoint implants, cardiac pacemakers and defibrillators, catheters orneurological electro-stimulation devices and medical systems such asdialysis equipment.

It is evident that these materials, when incorporated on consumer,commercial and medical products, will be exposed to considerableabrasion, mechanical impact and chemical agents used to clean andsanitize these products on a daily basis.

One advantage of ALD in the subject invention is its capability toengineer composite materials. In the case of photocatalytic titaniathose concepts were described above. Composite oxides of these types maybe formed either by co-deposition during a cation ALD deposition step orvia nano-laminates.

One other aspect of the subject invention is to further compositionallymodify the titania photocatalytic materials so as to increase themechanical hardness and chemical resistance of the surface. This may beaccomplished via ALD formation of nano-laminates that combine titaniawith Al2O3, SiO2, ZrO2, yttria stabilized zirconia (YSZ), or otheroxides that have desirable characteristics. In terms of hardness,titania is approximately 5.5-6.5 on the MHS hardness scale, while Al2O3is 9. Incorporation if intermittent Al2O3 ALD steps during ALD of thesubject titania photocatalytic materials, will increase the hardness andabrasion resistance of the antimicrobial or fluid purification activesurface.

In those cases Al2O3 may be formed, for example, using an ALD processthat is well known to those practiced in this field, for example usingtrimethylaluminum deposition with vapor phase water as the oxidizingco-reactant.

The present invention and some of its various embodiments are describedbelow, with reference to figures as necessary. Reference numbers areused to match particular elements described in the text with those shownin figures.

One embodiment is shown schematically in FIG. 1. This device 100 isdesigned to purify the air or other flowable medium at photocatalyticthin film surface 101 by oxidizing reactions with chemical andbiological contaminants. A transparent substrate 102 supports a thinfilm of the subject photocatalytic titania based material 101 on a frontsurface of substrate 102. In any embodiment of this invention, thisphotocatalytic thin film 101 may be on the substrate 102 and thereby indirect contact with the substrate 102, or may be over the substrate 102,having one or more intervening layers (not shown) disposed between thephotocatalytic thin film 101 and the substrate 102. In a preferredembodiment the photocatalytic material is a solid solution of TiO2-CeO2(90%/10%). The material has the anatase crystal structure.

The layer 101 is illuminated from its back surface, i.e. from thedirection of the substrate side 102 of the material. This back surfaceillumination may be accomplished using blue emitting LED sources, suchas those fabricated using the InGaN material system, with suitableemission wavelengths that induce the photocatalytic effect. In apreferred embodiment this wavelength may be approximately 420 nm. Othertypes of light sources and emission wavelength ranges may also be usedand are also the subject of the invention.

The back surface illumination may be through the thickness of thetransparent substrate, with illumination source 103, the emitted lightshown with the arrow and “hv” label. In a preferred embodiment the backsurfaced illumination may be near normal incidence. In that case theback substrate surface may be coated with an antireflection coating onsurface 104 to increase the illumination intensity incident on thephotocatalyst.

Back surface illumination may also be achieved by transmitting theillumination from source 105, into guiding modes in the transparentsubstrate, via coupling structures such as a surface relief grating 106.Alternatively, illumination via guiding modes may be accomplished byillumination of the substrate edges from source 107. Alternatively, thelight source 108 may be embedded in the transparent substrate. Thesetechniques may be used to substantially confine the optical radiation tothe interior of photocatalytic film 101.

The thickness of the layer 101 is sufficiently thin, e.g. in the rangeof 10-100 nm., for the illuminating wavelength to be optically absorbedthroughout the thickness of the photocatalyst including in the proximityof the outer surface. In that case the photocatalyst may becomechemically active and effective to drive oxidation reactions withcontaminants in the flowable medium in front of surface 101, therebypurifying the flowable medium.

FIG. 2 illustrates a similar configuration as FIG. 1 in which thetransparent substrate 201 has had a surface 202 roughened, which hassubsequently had the subject photocatalytic titania based thin film 203formed on that surface with a high degree of conformality, compositionand crystalline control. The material thickness may be accuratelycontrolled as needed to allow the back surface illumination from source204 to be absorbed throughout the layer 203 including in the proximityof its outer surface. Surfaces of this type may be used to increase thesurface area of the photocatalytic surface and enhance thephotocatalytic effect, thereby increasing the efficacy of the device topurify the ambient environment in front of photocatalytic surface 203.

Note that the substrate 201 may have its surface roughened 202, or thesubstrate surface may be flat and the surface of the photocatalytic film203 may be roughened (not shown), or any combination thereof. Theroughening of either the substrate or the film may be carried out bysubtractive techniques, such as but not limited to, wet etching, dryetching, sanding, machining, or bead blasting. The roughening of eitherthe substrate or the film may also be carried out by additive techniquessuch as, but not limited to, spray coating, powder coating, annealing,recrystallization, or nucleation or island formation before or during athin film deposition process. Roughening may be in a nanoscale ormicroscale.

The present invention also includes formation of titania based materialson physically shaped or textured surfaces that have specific affinity orspecific lethality for biologic impurities. For example certain microtopographies have been synthesized to mimic the topographic character ofshark skin, resulting in corresponding antibacterial properties.Addition of the subject titania based photocatalytic materials to thosesurfaces will add an antiviral effect to that surface. Other engineeredsurface topographies may attract or bind specific viruses or bacteriabased on the shape and spatial frequency power spectra of the surfacetopography. The subject titania photocatalytic materials andillumination schemes, or other photocatalytic materials, may be added tosuch surfaces to increase the microbe lethality and hence antimicrobialeffects there. These antimicrobial effects may include prevention ofbiofilms or reduction of bioburden i.e. residual microbes and fomitespresent after other cleaning or disinfection processes. Such surfacesthat combine microbe specific affinity surfaces with photocatalyticmaterials, may be used both as antimicrobial surfaces and for activepurification surfaces in the subject fluid purification apparatuses ofthe subject invention.

Photocatalyst devices of this type may be used to purify air nearmedical instruments or other tools, or for example as wall panels inrooms in which the photocatalytic illumination is provide from behindthe wall panel. It may also be used to purify the surfaces of thoseinstruments, or other high touch surfaces in hospitals, home or in theworkplace, to render them antimicrobial. Back surface illumination inthose cases may be provided by near UV or visible light LEDs or othersources with adequate spectral irradiancy at suitable wavelengths tostimulate the photocatalytic effect.

FIG. 3 illustrates an embodiment combining a lighting and flowable mediapurification system utilizing front surface illumination of the subjectphotocatalytic titania based material formed on a reflector. In thisembodiment 300, the titania based photocatalytic material 301 is appliedto the front surface of a pure metallic or dielectric enhanced metallicreflective surface 302, and is illuminated by a broadband light source303 such as a white LED that has significant optical emission in the UVor in the 400-450 nm. spectral regions. Alternatively the white lightsource may comprise any combination of red, green and blue wavelengths(“RGB”). While the metallic reflector has high reflectivity in thevisible spectral region, the reflectivity and E-field characteristics ofthe reflector at the photocatalytic illumination wavelengths, and thethickness of the photocatalytic layer, may be optimized to enhance thephotocatalytic effect, and hence the capability of the system to purifythe flowable medium between the light 303 and the photocatalytic thinfilm 301.

FIG. 4 illustrates a combined photocatalytic purifier and LED lightingsystem employing a titania based photocatalyst formed on a remotephosphor in an LED powered white light luminaire 400. In this case whitelight for illumination 401 is generated by irradiation of a remotephosphor layer 402 by a blue or UV light source 403. The remote phosphorlayer 402 is interposed between the metallic or dielectric enhancedmetallic high reflector 404, and titania based photocatalytic material405. Alternatively the photocatalytic material 405 may beheterogeneously incorporated onto the surface of remote phosphorparticles prior to their application in the luminaire system. Typicallythe short wavelength light source 403 for remote phosphor luminairesemits in the 460 nm. wavelength range. In cases where the photocatalyticeffect at thin film 405 requires a different wavelength, a second source406 may be included as needed to achieve the photocatalytic effect andpurification of the flowable media at surface 405. The photocatalyticeffecting source 403 may be operated intermittently, or during overnighthours for example as needed to regenerate the chemically activephotocatalytic surface.

FIG. 5 illustrates a flowable media purification function combined witha predominantly white lighting luminaire by utilizing a opticallytransmissive element that supports the subject titania photocatalyticmaterial. One possible configuration for the luminaire hasphotocatalytic illumination hv from source 501 incident on a broadbandluminaire metallic or dielectric enhanced metallic reflector 502 on amechanical support 503. The reflector coating 502 has averagereflectivity >80% in the visible spectral region (400-700 nm.wavelength), and >75% reflectivity for the photocatalytic illuminationwhich may be UV (<400 nm. wavelength), or visible light, such as in the400-500 nm portion of the visible spectrum. In a preferred embodiment,reflectivity is >90% in the visible spectral region (400-700 nm.wavelength), and >85% reflectivity for the photocatalytic illuminationwhich may be UV (<400 nm. wavelength), or visible light, such as in the400-500 nm. portion of the visible spectrum. In a further preferredembodiment, reflectivity is >95% in the visible spectral region (400-700nm. wavelength), and >90% reflectivity for the photocatalyticillumination which may be UV (<400 nm. wavelength), or visible light,such as in the 400-500 nm. portion of the visible spectrum. Saidreflected photocatalytic illumination is incident on a transmissivesupport 504 and then on the back surface of the photocatalytic material505. Ambient flowable media at the front or outer facing surface ofphotocatalytic material 505 and is thereby purified by oxidizingchemical reactions.

White light illumination from source 506 is also incident on thereflector 502/503, and may be reflected through the transmissive element504/505, for general illumination purposes. In another embodiment, abroadband antireflection coating may optionally be applied to the backsurface of 504 to increase external transmittance of that element.

It is noted that for certain photocatalytic material compositions 505,visible light illumination will stimulate the photocatalytic effect, andin those cases the functions of sources 501 and 506 may be achieved by asingle source or multiple sources of a single type.

FIG. 6 shows a combined photocatalytic purifier and lighting systemutilizing passive or convective means to exchange ambient fluids duringpurification. In an embodiment, a luminaire system 600 with light source601 is used in a decorative and light directing enclosure 602.Illumination from 601 is incident on the back surface of thetransmissive photocatalytic element 603 mounted on support or substrate604, and said illumination serves as both general illumination and asillumination to stimulate the photocatalytic effect. In this case thetitania based photocatalytic material is sensitive to visible lightemitted by 601. In a preferred embodiment, ambient air 605 is drawn upto the photocatalytic surface, across its chemically active surface, andupwards through the lamp body. The purified air 606 exits the assembly.Said gas flow through the assembly is driven by convective forces viaheating of the air around the light source 601, such as by waste heatfrom the source. Alternatively, if the support or substrate istransparent in the proper wavelength region, the photocatalytic materialmay be mounted on the side opposite the light source 601, facing thebottom opening of the enclosure 602, allowing the incoming air 605 tostrike the photocatalytic material directly.

FIG. 7 shows an embodiment 700 comprising an array of LED white lightemitters 701 in a decorative and light directing luminaire assembly 702.The array is mounted on an air permeable packaging material. In thiscase the outer surface 703 of the LED emitters 701 has the subjecttitania based photocatalytic material incorporated thereon, and thecomposition of said material has been adjusted such that visibleillumination from the white LEDs is suitable to stimulate thephotocatalytic effect. White light general illumination 704 is generatedby the luminaire. Ambient air 705 is drawn into, across and through theLED array by convective forces from waste heat from the LED array. In sodoing it is purified by chemical reactions at the photocatalyticsurfaces at each LED emitter. The purified air 706 passes upward and outof the top of the luminaire.

The subject invention may be embodied in the following examples that areby no means restrictive, but intended to illustrate the invention. Itwill be clear that the described invention is well adapted to achievethe purposes described above, as well as those inherent within. Thecitation of any publication is for its disclosure prior to the filingdate and should not be construed as an admission that the presentinvention is not entitled to antedate such publication by virtue ofprior invention. Numerous other changes may be made which will readilysuggest themselves to those skilled in the art and which are encompassedboth in the spirit of the disclosure above and the appended claims.

What is claimed is:
 1. A thin film photocatalytic material on asubstrate, the thin film photocatalytic material comprising titaniumoxide and constituents modifying two or more of the optical absorption,carrier recombination rate or photocatalytic characteristics of the thinfilm, the constituent chosen from the list of cation dopants, aniondopants, lanthanide series oxide, transition metal dopants and metallicnanoparticles.
 2. The material of claim 1, wherein the substrate has atleast one of high optical transmittance (>90%) or high opticalreflectance (>95%) for light wavelengths capable of stimulating aphotocatalytic effect in the thin film photocatalytic material.
 3. Thematerial of claim 1, wherein at least one constituent in thephotocatalytic thin film comprises an oxide of an element chosen fromthe group of La, Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Co, W,V, W, Zr, Cu, Mn, Fe Cr or from the anion group of N or C.
 4. Thematerial of claim 1, wherein the thin film photocatalytic materialincorporates metal particles, wherein the elements in the metalparticles are chosen from the group of Pt, Pd, Ru, Ir, Ag, Cu, Au, andFe.
 5. The material of claim 1, wherein the thin film photocatalyticmaterial is predominantly anatase crystal phase.
 6. The material ofclaim 1, wherein the thin film photocatalytic material has a thicknessin the range of 1-30 nm.
 7. The material of claim 1, wherein the thinfilm photocatalytic material has a thickness less than or equal to 5times the optical skin depth of the light wavelengths capable ofstimulating a photocatalytic effect in the thin film photocatalyticmaterial.
 8. The material of claim 1, wherein the thin filmphotocatalytic material is deposited by Atomic Layer Deposition.
 9. Thematerial of claim 8, wherein the constituents are incorporated in a nanolaminate structure.
 10. The material of claim 8, wherein thephotocatalytic thin film comprises a titanium oxide nano-laminate, whichmay include materials chosen from the group of suboxides to modifyoptical properties of the titanium oxide thin film and additional oxidesincluding Al2O3, SiO2, SiN, ZrO2, and yttria stabilized zirconia tomodify hardness or chemical properties of the thin film.
 11. Thematerial of claim 1, wherein the thin film photocatalytic material hasthickness variation of less than ±5% over the substrate.
 12. Thematerial of claim 1, wherein the surface area of the photocatalytic thinfilm is at least 1.5 times greater than it would be if the surfaceformed a simple geometric shape by using a combination of surfaceroughening and formation of the substrate into a complex geometricshape.
 13. The material of claim 1, wherein the substrate is comprisedof a material chosen from the group of fused silica, glass, silicacontaining glass, inorganic or polymeric materials or other materialswith low optical absorption at the photocatalytic illuminationwavelength.
 14. The material of claim 13, wherein the substrate has highporosity with a surface area greater than 50 square meters per gram. 15.A method of forming a photocatalytic thin film on a high surface areasubstrate, comprising; choosing a substrate material with opticaltransparency above 80% at optical wavelengths suitable for stimulationof a photocatalytic effect in a photocatalytic thin film; forming thesubstrate material into a substrate having a complex geometric shape,the shape having high surface area; placing the substrate into a chambercapable of providing a controlled atmosphere at low pressure; removingthe air from the chamber and providing a controlled atmosphere; anddepositing a photocatalytic thin film comprising titanium oxide.
 16. Themethod of claim 15, wherein depositing the photocatalytic thin filmproduces a thin film in which the thickness variation of thephotocatalytic material is less than ±5% over the active area of thedevice.
 17. The method of claim 15, wherein an additional step comprisesdepositing on the substrate at least one coating to modify its opticalproperties.
 18. The method of claim 15, wherein depositing thephotocatalytic thin film is carried out until it reaches a thickness inthe range of 1-30 nm.
 19. The method of claim 15, wherein depositing thephotolytic thin film takes place on a substrate wherein a combination ofroughening the substrate surface and forming the substrate into acomplex geometric shape increases the surface area of the photocatalyticthin film to at least 1.5 times greater than it would be if the surfaceformed a simple geometric shape.
 20. The method of claim 15, whereinthat method is Atomic Layer Deposition.
 21. The method of claim 20,wherein the substrate has a high degree of open cell porosity, withsurface area greater than 50 square meters per gram.
 22. The method ofclaim 15, wherein depositing the photolytic thin film comprises addinglanthanide elements during deposition.
 23. The method of claim 15,wherein depositing the photocatalytic thin film comprises incorporatingan oxide of an element chosen from the group of La, Ce, Pr, Nd, Pm, Eu,Gd, Tb, Dy, Ho, Er, Tm, Yb, Co, W, V, W, Zr, Cu, Mn, Fe Cr or from theanion group of N or C.
 24. The method of claim 15, wherein depositingthe photocatalytic thin film comprises incorporating metal particlesduring deposition, wherein the elements in the metal particles arechosen from the group of Pt, Pd, Ru, Ir, Ag, Cu, Au, and Fe.